A midden mound is a trash dump formed by the accumulation of refuse where American Indians once lived, rather than a mound purposely built for a specific use. Unlike ceremonial mounds, middens contain materials that reflect daily domestic life, including broken tools used in food preparation and the bones of animals that had been eaten. Excavations at the Pocahontas site have identified a number of midden areas, including a prominent mounded area, while other midden areas were destroyed by construction of the northbound lanes of Highway 49. For archaeologists, middens are important because they preserve artifacts and food remains such as charred plants, animal bone, and mussel shell. Their soils contain high levels of phosphates from decomposed organic matter, which lowers acidity and helps preserve fragile organic materials. Another form, the sheet midden, consists of a dark, organically enriched layer of soil spread across a broad area rather than heaped into a mound, often where an American Indian village once stood, formed by trash that accumulated in and around village houses.